How much potassium bromide as anti-fog?

Discussion in 'B&W: Film, Paper, Chemistry' started by 2F/2F, Dec 12, 2009.

  1. 2F/2F

    2F/2F Member

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    Hello,

    How much potassium bromide can/should I add per liter of paper developer to try to minimize fog to a great degree?

    How much benzotriazole?

    Can I use both together?

    Are there certain paper developers that are better for these techniques than others?

    Thank you.
     
  2. Photo Engineer

    Photo Engineer Subscriber

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    The amounts of these antifoggants vary depending on the paper emulsion. They also vary in each developer.

    Therefore, you can state an amount with Dektol 1:2, or 1:3 with Ilford MGIV and it might be wrong with Slavich or Oriental. Generally, about 0.5 - 1 g/l of Bromide will do the trick depending on the fog level. You may want to go as high as 2 g/l, but with a high Chloride paper the Bromide will have a different efect than on a low Chloride paper.

    With BTAZ, you can use between 10 mg and 100 mg/l to start with and then go up.

    You can combine both antifoggants.

    They will affect the tone of the imgage.

    PE
     
  3. Ian Grant

    Ian Grant Subscriber

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    Don't use Benzotriazole with a warm tone paper/warm tone developer unless you want colder tones, and adding more bromide will make a warm tone paper warmer still.

    In practice it's warm tone papers that tend to fog fastest with age, particularly those with no Cadmium made from the 90's (approx) onwards. Bromide papers respond better to anti-foggants to combat base fog due to aging, but many will keep decades only losing speed and contrast remaining free of fog.

    Ian